At this time, there is a paucity of academic literature that specifically examines the effectiveness of single and multi-stream recycling. What little work has been done in this area has generally been “grey literature” – consulting reports, trade magazine articles, technical papers etc. – carried out by local governments. Much of the information that is currently available comparing multi and single stream programs has reflected either local circumstances that can differ substantially from one area to the next and/or has reflected a particular focus or interest of the author. As a result, this research attempted to expand the research focus to the greatest extent possible to include system performance documented both inside and outside Ontario, and to identify the specific rationale supporting the findings regarding system performance.
There is a general consensus in the available literature that single stream recycling offers potential for more efficient collection and reduced collection costs. In 2007, the Solid Waste Association of North America (SWANA) observed that collection savings from single stream systems ranged from $10 to $20 per tonne. Similar findings were observed by The Solid Waste Hazardous Waste Education Centre at the University of Wisconsin, which reported that the potential savings associated with single stream collection can vary from 5% to 25%. In contrast to these findings, an examination of the collection costs by Cascades/Metro Waste concluded that the savings from single stream collection was much lower, with estimates ranging from $0 to $3 a tonne (2008)
While single stream collection costs are presumed to be lower than multi stream systems, it is generally accepted and demonstrated that the capital and operating costs for single stream processing are more expensive. In a study by the University of Wisconsin, processing costs for single stream systems were 10% higher on average when compared to multi stream systems (2005). These findings were echoed in studies by Waukesha County (2007) and Escambria County (2008), which observed differences in processing costs ranging from 7% to 50% (with single stream systems being more expensive). However, there have been some studies that have estimated that the annual operating cost for single stream facilities could be lower than a multi stream facility when operating at the same throughput. A study undertaken by consulting firm Stantec Ltd., it was estimated that the costs for a hypothetical facility with a throughput of 14 tonnes per hour would be $107/tonne for a single stream system and $116/tonne for a multi stream system (2012).
Reports evaluating the effectiveness of single stream recycling systems have also found that the commodities recovered from single stream programs are of lower quality than those recovered from multi stream systems. This results in decreased value and/or difficulties in finding end-markets. In a study conducted by Morawski (2010), it was found that single stream systems had eight times the yield loss compared to multi stream systems for paper fibers collected curbside. Plastics processors reported that material from single stream MRFs had a yield rate 10% lower than multi stream MRFs (Morawski, 2010).